Secondary batteries are widely utilized not only as a substitute for a primary battery but also as a power source for electronic apparatuses such as mobile phones and IT devices. In particular, non-aqueous electrolyte secondary batteries, typically exemplified by a lithium ion secondary battery, have been increasingly applied to electric vehicles and large-scale industrial machines, because of the capability of providing high energy density. Further, to obtain an even higher voltage, non-aqueous electrolyte secondary batteries, which are battery cells, are stacked to constitute a battery module.
Such a battery module is generally placed in a single container. An example of the container can be found in Patent Literature 1 for example, which discloses a power source unit including a housing serving as the container that accommodates therein a battery module composed of a plurality of battery cells (see FIG. 12 of PTL 1).